One savvy Reddit user seems to think so! Also: hoards of other disgruntled and/or confused customers, according to Google. The scam? Charter's convincing customers that their perfectly good router hardware—including the Linksys WRT54G—just doesn't work with the ISP.

I use a LinkSys router. I've had it set up and working perfectly for over a year. Well, the past few months, we've had several disconnects from Charter. We're paying for 10mbps service, but for the past week straight it would not go above 2mbps, and that's if it worked at all. We called Charter, and they had us plug the modem directly into the machine and Voila! over 20mbps speeds!

I suspected that they might have blocked the spectrum of Linksys MAC addresses, so I cloned my PC's MAC address to the Linksys and it INSTANTLY connected. Our bad, out of date, incompatible Linksys router suddenly is getting the 20mbps speeds that our PC's were getting.

I'm not sure about the specific allegation that they've completely blocked Linksys routers' MAC addresses, since there do seem to be other—though obscure—ways to work around the issue, but this kind of thing (router blocking, specifically) is far from unheard of even for major ISPs. Charter's service does make it severely inconvenient for a computer-savvy person (or impossible for your average customer) to user popular router hardware that they already own, pushing them to rent or buy sanctioned, official router hardware like this, which probably isn't any more capable the the old WRT54G piece you've got sitting behind your desk already:

There's a small chance this is all some kind of misunderstanding, but with plenty of similar stories scattered around the internet alleging the exact same thing—sudden connection failure, then a hard sell for a new router over the phone—it's hard to imagine Charter coming out of this looking good. [Reddit]